Scarcity and increasing costs of fossil fuels have caused increased interest in sustainable synthesis strategies. In this respect, synthesis of chemical basic materials which typically are obtained from petrochemical refinement, are of special interest. Significant efforts have been taken for developing alternative synthesis strategies in order to meet the needs of the chemical industry also in the future. An especially successful concept in this respect is biorefinement. “biorefinement” refers to a technical method for purifying, refining, separating and/or concentrating of individual raw materials from a biomass, wherein renewable primary products are considered a “biomass”. On the other hand, fossil energy sources obtained from biomass are not considered renewable primary products. Biomass generally contains about 35 to 50% cellulose, 25 to 30% hemicellulose and 25 to 30% lignin. Hemicellulose is a general term for mixtures of polysaccharides present in herbal biomass. By way of biorefinement saccharide such as glucose, xylose and fructose can be obtained.
The present invention relates to the manufacture of furan compounds from saccharides. In this respect the invention describes a simple and costs effective method for the manufacture of furan compounds in the presence of a heterogeneous catalyst. Furan compounds are of special interest, since they are valuable intermediates in the manufacture of polymers, solvents, pharmaceutical products, fine chemicals, fuels, fertilizers and herbicides. In most cases there are high requirements regarding purity of the required furan compounds.
Manufacture of furan compounds from renewable primary products is known and has been put into technical practice. The manufacture of furan compounds, especially of furfural and 5-hydroxymethylfurfural is, however, difficult, since consecutive reactions lead to various degradation products. In known methods for the manufacture of furan compounds homogeneous catalysts are used. “Homogeneous catalysts” are catalyst systems in which the catalyst and the educt are present in the same phase. In the known methods inorganic acids are normally used as catalysts. For example, the manufacture of furan compounds in the presence of homogeneous acids, especially inorganic homogeneous acids such as sulphuric acid, phosphoric acid or hydrochloride acid, is described in “Reactions of d-fructose in water at temperatures up to 400° C. and pressures up to 100 MPa, Aida T. M. et al., Journal of Supercritical Fluids 2007, 42(1), 110-119.
In view of the use of homogeneous catalysts a laborious and cost intensive work-up is necessary. For example, acids first have to be neutralized in order to stop the reaction and further work-up is made possible. In addition, in known methods organic solvents, ionic fluids or supercritical fluids are used, which further complicates work-up an increases production costs. In particular, the use of organic solvents and other adjuvant has a negative effect on the purity of the obtained furan compounds.
Therefore, there is a need for new catalysts, catalyst systems or reaction systems for improving the manufacture of furan compounds. In this respect it is of special interest to optimized the manufacturing process in order to achieve a lower product prize.